Heat Exchanger Tube, Heat Exchanger, and Manufacturing Method Thereof

ABSTRACT

This invention relates to a method of manufacturing an aluminum heat exchanger tube. In forming a thermally sprayed layer  21  on a surface of an aluminum flat tube by thermally spraying Al—Si alloy thermal-spraying particles, quenching the thermally sprayed thermal-spraying particles in a molten state to make them adhere to the tube core  2   a . The surface of the thermally sprayed layer  21  is smoothed with, e.g., reduction rolls to form a brazing layer  20 . With this method, brazing defects due to fin detachment, erosion to the tube of the brazing material, etc., can be prevented, resulting in good brazing performance.

This application claims priority under 35 U.S.C. §119 to Japanese PatentApplication No. 2004-113784 filed on Apr. 8, 2004 and U.S. ProvisionalApplication No. 60/561,903 filed on Apr. 14, 2004, the entiredisclosures of which are incorporated herein by reference in theirentireties.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is an application filed under 35 U.S.C. §111(a)claiming the benefit pursuant to 35 U.S.C. §119(e)(1) of the filing dateof U.S. Provisional Application No. 60/561,903 filed on Apr. 14, 2004,pursuant to 35 U.S.C. §111(b).

TECHNICAL FIELD

The present invention relates to an aluminum heat exchanger used for,for example, a refrigeration cycle for car air-conditioners, a tube forsuch heat exchangers, and a method of manufacturing the same.

In this disclosure including claims, the wording of “aluminum” denotesaluminum and its alloy.

BACKGROUND ART

The following description sets forth the inventor's knowledge of relatedart and problems therein and should not be construed as an admission ofknowledge in the prior art.

As an aluminum heat exchanger for use in a refrigeration cycle for carair-conditioners, the so-called multi-flow type or parallel flow typeheat exchanger 51 as shown in FIG. 5 is well-known. In this heatexchanger, a plurality of flat tubes 52 are arranged in the thicknessdirection with a corrugated fin 53 interposed therebetween, and hollowheaders 54 are connected to the ends of the tubes 52 in fluidcommunication.

In manufacturing such a heat exchanger 51, commonly, heat exchangercomponents are fabricated into a provisional assembly, and then theassembly is integrally brazed in a furnace. As a method of forming abrazing layer, as disclosed by Patent Document 1 (Japanese UnexaminedLaid-open Patent Publication No. S59-10467) for example, it iswell-known that brazing alloy is thermally sprayed onto a surface of analuminum heat exchanger tube.

In cases where a brazing alloy is thermally sprayed onto a surface of aheat exchanger tube 52 to form a brazing material layer, however,unevenness of the brazing material layer is large, and therefore abrazing layer contracts after the brazing. As a result, asexaggeratingly shown in FIG. 5, some joining scheduled portions betweenthe heat exchanger tube 52 and the fin 53 may become un-joinedcontinuously along the longitudinal direction of the tube 52, which maycause a poor brazed portion such as the so-called fin detachment.

To solve the problem, conventionally, various technique have beenproposed. For example, Patent document 2 (JP, H11-33709,A) discloses atechnique in which a brazing alloy is thermally sprayed onto a streakedsurface of a heat exchanger tube (tube core) to thereby form a brazinglayer. Patent document 3 (JP, H06-200344,A) discloses a technique inwhich at the time of thermally spraying brazing alloy powder the brazingpowder is thermally sprayed on a surface of a heat exchanger tube in astate in which non-fused structure remains partially without completelyfusing the alloy powder.

In the technique in which streaked irregularities are formed on thesurface of the tube core, however, capillary force will be generatedalong the streaked irregularity portions causing an easy flow of thefused brazing material on the tube surface during the brazing. This inturn generates erosion of the tube by the brazing material, resulting inpoor brazing.

In the technique in which the brazing alloy powder is thermally sprayedin a state in which non-fused structure remains partially, in caseswhere, for example, the thermally spraying particle size is large, acavity will be formed between particles thermally sprayed on the tubesurface. This causes deteriorated volume rate (filling rate) of thesubstantial brazing material (net thermally sprayed layer) in the entirethermally sprayed layer (apparent thermally sprayed layer) including thecavity. As a result, the actual amount of brazing material tends todecrease. Thus, there is a room to be improved.

The description herein of advantages and disadvantages of variousfeatures, embodiments, methods, and apparatus disclosed in otherpublications is in no way intended to limit the present invention.Indeed, certain features of the invention may be capable of overcomingcertain disadvantages, while still retaining some or all of thefeatures, embodiments, methods, and apparatus disclosed therein.

Other objects and advantages of the present invention will be apparentfrom the following preferred embodiments.

DISCLOSURE OF INVENTION

The preferred embodiments of the present invention have been developedin view of the above-mentioned and/or other problems in the related art.The preferred embodiments of the present invention can significantlyimprove upon existing methods and/or apparatuses.

The present invention was made in view of the aforementionedconventional technology, and aims to provide a heat exchanger tubecapable of preventing occurrence of poor brazing due to fin detachmentor erosion of a tube by brazing material and attaining good brazing, aheat exchanger and a method of manufacturing them.

To attain the aforementioned objects, the structure of the presentinvention can be summarized as follows.

[1] A method of manufacturing an aluminum heat exchanger tube, themethod comprising the steps of:

in forming a thermally sprayed layer on a surface of an aluminum flattube by thermally spraying Al—Si alloy thermal-spraying particles,quenching the thermally sprayed thermal-spraying particles in a moltenstate to make them adhere to the tube core; and

smoothing a surface of the thermally sprayed layer to form a brazinglayer.

The aluminum heat exchanger tube obtained by the manufacturing method ofthis invention will be combined with and brazed to, for example, analuminum fin. At this time, good brazing performance can be secured.

That is, in the heat exchanger tube obtained by the manufacturing methodof this invention, the surface of the thermally sprayed layer formed bythermally spraying alloy is smoothed to obtain a brazing layer.Therefore, a fin can be joined in a balanced manner over the entiresurface of the brazing layer, which assuredly prevents poor joining suchas fin detachment.

Furthermore, in this invention, since the thermally sprayed layer issmoothed to form the brazing layer, the smoothing enhances the brazingmaterial filling rate of the brazing layer, resulting in a sufficientamount of the brazing material as the brazing layer, which can assuredlyprevent poor brazing due to shortage of brazing material.

Furthermore, in this invention, since the molten thermal-sprayingparticles are quenched, moderate brittleness can be given to thethermally sprayed layer as compared with the case where thermal sprayingis performed in a state in which the thermal-spraying particles arepartially in a non-molten state and where the thermal-spraying particlesare not quenched but gradually cooled. For this reason, when thethermally sprayed layer is formed into the brazing layer by smoothingthe thermally sprayed layer, only the thermally sprayed layer can beassuredly formed into a desired state. Thus, for example, thedeformation of the tube core can be prevented effectively, resulting inhigh quality.

In this invention, “melting” of the thermal-spraying particles can beperformed by adjusting the thermal-spraying temperature to 3,000° C. orabove, preferably 3,500° C. or above, more preferably 4,000° C. orabove, still more preferably 4,500° C. or above. In cases where an arcspraying method is employed, “melting” of the thermal spraying particlescan be performed more assuredly. In this invention, especially in caseswhere the thermal-spraying temperature is set to a high temperature, itis considered that smoothing of the thermally sprayed layer can beexecuted effectively. That is, in the case of high temperature thermalspraying, it is considered that the thermal-spraying particles decreasein size, the cooling rate increases, the quickly cooled small sizedthermal-spraying particles accumulate on the tube surface to form adesired brittle structure as the thermally sprayed layer, which enableseffective smoothing of the thermally sprayed layer.

Moreover, in this invention, by adjusting the temperature differencebetween the thermal-spraying particles in a molten state and thethermal-spraying particles reached the tube core in a cooled state to2,500° C. or more, preferably 3,000° C. or more, more preferably 3,500°C. or more, and/or by performing the thermal spraying at thethermal-spraying distance of 30 to 150 mm by an arc thermal sprayingmethod, “quenching” of the thermal-spraying particles can be performed.

[2] The method of manufacturing an aluminum heat exchanger tube asrecited in the aforementioned Item 1, wherein surface roughness (Ry) ofthe tube core is adjusted to less than 10 μm.

In this invention, since the surface of the tube core is formed into asmooth surface, the brazing layer can be stably secured to a widesurface area of the tube core. Thus, it is possible to effectivelyprevent unexpected flow of the molten brazing material on the surface ofthe tube core during the brazing, which can assuredly prevent defects,such as erosion to the tube core of the brazing material.

[3] The method of manufacturing an aluminum heat exchanger tube asrecited in the aforementioned Item 1 or 2, wherein surface roughness(Ry) of the brazing layer is adjusted to less than 50 μm.

In this invention, since the surface of the brazing layer is smoothed, afin can be brazed to the brazing layer assuredly, which more assuredlyprevents occurrence of brazing defects such as fin detachment.

[4] The method of manufacturing an aluminum heat exchanger tube asrecited in any one of the aforementioned Items 1 to 3, wherein athermal-spraying temperature of the thermal-spraying particles isadjusted to 3,000° C. or above.

In this invention, melting of the thermal-spraying particles can beassuredly attained in the thermal spraying processing.

[5] The method of manufacturing an aluminum heat exchanger tube asrecited in any one of the aforementioned Items 1 to 4, wherein thethermal-spraying particles are cooled to 800° C. or below after reachingthe tube core.

In this invention, quenching of the thermal-spraying particles can besmoothly performed at the time of the thermal spraying.

[6] The method of manufacturing an aluminum heat exchanger tube asrecited in any one of the aforementioned Items 1 to 5, wherein inthermally spraying the thermal-spraying particles, a temperaturedifference between the thermal-spraying particles in a molten state andthe thermal-spraying particles reached the tube core in a cooled stateis adjusted to 2500° C. or more.

In this invention, quenching of the thermal-spraying particles can beassuredly performed at the time of the thermal spraying.

[7] The method of manufacturing an aluminum heat exchanger tube asrecited in any one of the aforementioned Items 1 to 6, wherein inthermally spraying the thermal-spraying particles, the thermal-sprayingparticles reached the tube core is cooled by releasing the heat to thetube core.

In this invention, quenching of the thermal-spraying particles can bemore smoothly performed at the time of the thermal spraying.

[8] The method of manufacturing an aluminum heat exchanger tube asrecited in any one of the aforementioned Items 1 to 7, wherein anaverage equivalent diameter of Si crystallization particles in thethermally sprayed layer is adjusted to 1 μm or less.

In this invention, melting and quenching of the thermal-sprayingparticles are assuredly performed at the time of the thermal spraying.

[9] The method of manufacturing an aluminum heat exchanger tube asrecited in any one of the aforementioned Items 1 to 8, wherein anapparent volume rate (filling rate) of the brazing material in thebrazing layer is adjusted to 40% or more.

In this invention, a sufficient amount of the brazing material can besecured in the brazing layer, which in turn can assuredly preventoccurrence of brazing defects due to shortage of brazing material.

[10] The method of manufacturing an aluminum heat exchanger tube asrecited in any one of the aforementioned Items 1 to 9, wherein inthermally spraying the thermal-spraying particles, a thermal-sprayingdistance from a spraying position of the thermal-spraying particles toan adhering position on the tube core is adjusted to 30 to 150 mm.

In this invention, quenching, etc., of thermal-spraying particles can beperformed more assuredly.

[11] The method of manufacturing an aluminum heat exchanger tube asrecited in any one of the aforementioned Items 1 to 10, wherein thermalspraying of the thermal-spraying particles is performed by an arcspraying method.

In this invention, melting, etc., of the thermal-spraying particles canbe performed more assuredly.

[12] The method of manufacturing an aluminum heat exchanger tube asrecited in any one of the aforementioned Items 1 to 11, wherein a Sicontent in the thermally sprayed layer is adjusted to 6 to 15 mass %.

In this invention, a brazing layer further improved in brazingperformance can be formed.

[13] The method of manufacturing an aluminum heat exchanger tube asrecited in any one of the aforementioned Items 1 to 12, wherein anaverage thickness of the brazing layer is adjusted to 3 to 50 μm.

In this invention, a stable brazing layer can be formed.

[14] The method of manufacturing an aluminum heat exchanger tube asrecited in any one of the aforementioned Items 1 to 13, wherein thesurface of the thermally sprayed layer is pressed with reduction rollsto smooth the surface.

In this invention, smoothing of the thermally sprayed layer can beperformed continuously, improving the working efficiency.

[15] The method of manufacturing an aluminum heat exchanger tube asrecited in any one of the aforementioned Items 1 to 14, wherein Zn iscontained to the thermally sprayed layer.

In this invention, a sacrificial protection layer can be formed on thetube surface.

[16] The method of manufacturing an aluminum heat exchanger tube asrecited in any one of the aforementioned Items 1 to 15, wherein Zn andCu are contained to the thermally sprayed layer.

In this invention, a sacrificial protection layer can be formed on thetube surface, and the potential of the tube surface can also beadjusted.

[17] The method of manufacturing an aluminum heat exchanger tube asrecited in any one of the aforementioned Items 1 to 16, wherein the tubecore is formed by extrusion, and the thermal-spraying particles arethermally sprayed to the tube core immediately after the extrusion.

In this invention, a desired thermally sprayed layer can be formedassuredly in an efficient manner, which in turn can form a desiredbrazing layer assuredly and efficiently.

[18] The method of manufacturing an aluminum heat exchanger tube asrecited in any one of the aforementioned Items 1 to 17, wherein eachthermal-spraying particle adheres to the surface of the tube core in aflat state.

In this invention, quenching of the thermal-spraying particles can beperformed efficiently.

[19] The method of manufacturing an aluminum heat exchanger tube asrecited in any one of the aforementioned Items 1 to 18, wherein thethermal-spraying particles are thermally sprayed under a non-oxidizingatmosphere.

In this invention, forming of an oxide film on the thermal-sprayingparticles can be prevented, which enables formation of a stablethermally sprayed layer.

[20] A method of manufacturing an aluminum heat exchanger tube, themethod comprising the steps of:

in forming a thermally sprayed layer on a surface of an aluminum flattube by thermally spraying Al—Si alloy thermal-spraying particles,thermally spraying the thermal-spraying particles to a tube core by anarc spraying method, and quenching the thermally sprayedthermal-spraying particles to 800° C. or below; and

smoothing a surface of the thermally sprayed layer to form a brazinglayer.

In the heat exchanger tube obtained by the manufacturing method of thisinvention, in the same manner as mentioned above, the brazing layer isobtained by smoothing the surface of the thermally sprayed layerobtained by the thermal spraying of brazing alloy. A fin can be brazedto the brazing layer assuredly, which more assuredly prevents occurrenceof brazing defects such as fin detachment.

Furthermore, in this invention, since the brazing layer is formed bysmoothing the thermally sprayed layer, the smoothing can increase thebrazing material filling rate of the brazing layer, a sufficient amountof brazing material in the brazing layer can be secured, which assuredlycan prevent brazing defects due to shortage of brazing material.

Furthermore, in this invention, molten thermal-spraying particles arethermally sprayed on the tube core by an arc spraying method and thesprayed thermal-spraying particles are quenched to a predeterminedtemperature or below. Therefore, moderate brittleness can be given tothe thermally sprayed layer as compared with the case where thermalspraying is performed in a state in which the thermal-spraying particlesare partially in a non-molten state and where the thermal-sprayingparticles are not quenched but gradually cooled. For this reason, whenthe thermally sprayed layer is formed into the brazing layer bysmoothing the thermally sprayed layer, only the thermally sprayed layercan be assuredly formed in a desired state. Thus, for example, thedeformation of the tube core can be prevented effectively, resulting inhigh quality.

[21] A method of manufacturing an aluminum heat exchanger tube, themethod comprising the steps of:

in forming a thermally sprayed layer on a surface of an aluminum flattube by thermally spraying Al—Si alloy thermal-spraying particles,performing the thermal spraying by an arc spraying method in which athermal-spraying distance from a spraying position of thethermal-spraying particles to an adhering position on the tube core isadjusted to 30 to 150 mm; and

smoothing a surface of the thermally sprayed layer to form a brazinglayer.

In the heat exchanger tube obtained by the manufacturing method of thisinvention, good brazing performance can be secured in the same manner asmentioned above.

Furthermore, in this invention, molten thermal-spraying particles arethermally sprayed to the tube core by an arc spraying method, and thethermal-spraying particles are sprayed to tube core with high kineticenergy to thereby be deformed into a flat shape and quenched. Therefore,in the same manner as in the above-mentioned case, a heat exchanger tubeof high quality can be secured.

[22] A method of manufacturing an aluminum heat exchanger tube, themethod comprising the steps of:

in forming a thermally sprayed layer on a surface of an aluminum flattube by thermally spraying Al—Si alloy thermal-spraying particles,thermally spraying the thermal-spraying particles with athermal-spraying temperature of 3,000° C. or above and cooling them to800° C. or below to make them adhere to a tube core; and

smoothing a surface of the thermally sprayed layer to form a brazinglayer.

In the heat exchanger tube obtained by the manufacturing method of thisinvention, in the same manner as mentioned above, good brazingperformance can be secured.

Furthermore, in this invention, molten thermal-spraying particles aresprayed to the tube core at a high temperature, and the sprayedthermal-spraying particles are quenched at a temperature below apredetermined temperature. Therefore, in the same manner as mentionedabove, high quality heat exchanger tube can be provided.

[23] A method of manufacturing an aluminum heat exchanger tube, themethod comprising the steps of:

in forming a thermally sprayed layer on a surf ace of an aluminum flattube by thermally spraying Al—Si alloy thermal-spraying particles,thermally spraying the thermal-spraying particles in a molten state andcooling to make them adhere to a tube core, and adjusting a temperaturedifference between the thermal-spraying particles in a molten state andthe thermal-spraying particles after the cooling is adjusted to 2,500°C. or more; and

smoothing a surface of the thermally sprayed layer to form a brazinglayer.

In the heat exchanger tube obtained by the manufacturing method of thisinvention, in the same manner as mentioned above, good brazingperformance can be secured.

Furthermore, in this invention, since molten thermal-spraying particlesare sprayed to the tube core and the sprayed thermal-spraying particlesare quenched, in the same manner as mentioned above, high quality heatexchanger tube can be provided.

[24] An aluminum heat exchanger tube manufactured by the method asrecited in any one of the aforementioned Items 1 to 23.

The heat exchanger tube of this invention is obtained by theaforementioned manufacturing method of this invention, and therefore inthe same manner as mentioned above, good brazing performance and highquality can be secured.

[25] An aluminum heat exchanger tube, comprising:

an aluminum flat tube core; and

a thermally sprayed layer formed on a surface of the tube core bythermally spraying thermal-spraying particles of molten Al—Si alloy,

wherein a surface of the thermally sprayed layer is smoothed to form abrazing layer, and

wherein an average equivalent diameter of Si crystallization particlesin the thermally sprayed layer is adjusted to 1 μm or less.

In the heat exchanger tube of this invention, since the brazing layer isformed by smoothing the thermally sprayed layer, in the same manner asmentioned above, good brazing performance can be secured.

Moreover, since the Si crystallization in the thermally sprayed layer issmall, it is possible to confirm the melting and quenching of thethermal-spraying particles at the time of the thermal spraying, andtherefore a heat exchanger tube of high quality can be obtained.

[26] The aluminum heat exchanger tube as recited in the aforementionedItem 25, wherein an apparent volume rate (filling rate) of the brazingmaterial in the brazing layer is adjusted to 40% or more.

In the heat exchanger tube of this invention, since the filling rate ofthe brazing material in the brazing layer is high, a sufficient amountof brazing material can be secured, and further improved brazingperformance can be secured.

[27] An aluminum heat exchanger including aluminum heat exchanger tubesand aluminum fins brazed to the tubes in an assembled state, wherein theheat exchanger tubes are manufactured by the method as recited in anyone of the aforementioned Items 1 to 23.

Since this specifies a heat exchanger equipped with a heat exchangertube as a main component obtained by the aforementioned method of theinvention, in the same manner as mentioned above, the same functions andresults can be secured.

[28] An aluminum heat exchanger including a pair of aluminum headers anda plurality of heat exchanger tubes arranged in a longitudinal directionof the header with a fin interposed therebetween, end portions of theheat exchanger tubes being communicated with the headers,

wherein the heat exchanger tubes are manufactured by the method asrecited in any one of the aforementioned Items 1 to 23.

This invention specifies the so-called parallel-flow type or multi-flowtype heat exchanger equipped with the heat exchanger tubes obtained bythe aforementioned manufacturing method of the invention as maincomponents. Therefore, in the same manner as mentioned above, the samefunctions and results can be secured.

[29] A method of manufacturing an aluminum heat exchanger, the methodcomprising:

a step of preparing an aluminum heat exchanger tube manufactured by themethod as recited in any one of the aforementioned Items 1 to 23;

a step of preparing an aluminum fin; and

a step of brazing the heat exchanger tube and the fin in an assembledstate.

In this invention, since the heat exchanger is manufactured using theheat exchanger tube obtained by the aforementioned manufacturing methodof the invention, in the same manner as mentioned above, the samefunctions and results can be secured.

[30] A method of manufacturing an aluminum heat exchanger, the methodcomprising:

a step of preparing a plurality of aluminum heat exchanger tubesmanufactured by the method as recited in any one of the aforementionedItems 1 to 23;

a step of preparing a plurality of aluminum fins;

a step of preparing a pair of headers;

a step of obtaining a provisional assembly in which the plurality ofheat exchanger tubes arranged in a longitudinal direction of the headerwith the fin interposed therebetween are assembled with the headers withend portions of each heat exchanging tube communicated with the headers;

a step of integrally brazing adjacent heat exchanger tubes and the finsby simultaneously brazing the provisional assembly.

In this invention, the so-called parallel-f low type or multi-flow typeheat exchanger is manufactured by using the heat exchanger tubesobtained by the aforementioned manufacturing method of the invention.Therefore, in the same manner as mentioned above, the same functions andresults can be secured.

[31] A refrigeration cycle in which refrigerant compressed by acompressor is condensed with a condenser, and the condensed refrigerantis decompressed by passing through a decompressor, and the decompressedrefrigerant is evaporated with an evaporator and returned to thecompressor,

wherein the condenser is constituted by the aluminum heat exchanger asrecited in the aforementioned Item 28.

In the refrigeration cycle of this invention, the same effects can bedemonstrated.

EFFECTS OF THE INVENTION

As mentioned above, according to the present invention, brazing defectsdue to fin detachment, erosion to the tube of brazing material, etc.,can be prevented, and therefore good brazing performance can be secured.

The above and/or other aspects, features and/or advantages of variousembodiments will be further appreciated in view of the followingdescription in conjunction with the accompanying figures. Variousembodiments can include and/or exclude different aspects, featuresand/or advantages where applicable. In addition, various embodiments cancombine one or more aspect or feature of other embodiments whereapplicable. The descriptions of aspects, features and/or advantages ofparticular embodiments should not be construed as limiting otherembodiments or the claims.

BRIEF DESCRIPTION OF DRAWINGS

The preferred embodiments of the present invention are shown by way ofexample, and not limitation, in the accompanying figures, in which:

FIG. 1 is a front view showing an aluminum heat exchanger according toan embodiment of this intention;

FIG. 2 is an enlarged perspective view showing joined portions of thetubes and fins in the heat exchanger of the aforementioned embodiment;

FIG. 3A is an enlarged cross-sectional view showing a tube coreimmediately after thermal spraying during a manufacturing process of theheat exchanger tube according to the embodiment, and FIG. 3B is anenlarged cross-sectional view showing the tube core immediately aftersmoothing of the thermally sprayed brazing material;

FIG. 4A is an enlarged cross-sectional view showing a tube coreimmediately after thermal spraying in a manufacturing process of theheat exchanger tube, which is an example outside the scope of theinvention, and FIG. 4B is an enlarged cross-sectional view showing thetube core immediately after smoothing of the tube core; and

FIG. 5 is a front view showing a conventional heat exchanger in whichfin detachment occurred due to brazing.

BEST MODE FOR CARRYING OUT THE INVENTION

In the following paragraphs, some preferred embodiments of the inventionwill be described by way of example and not limitation. It should beunderstood based on this disclosure that various other modifications canbe made by those in the art based on these illustrated embodiments.

FIG. 1 is a front view showing an aluminum heat exchanger 1 which is anembodiment of this invention. As shown in this figure, this heatexchanger 1 is used as a condenser for use in a refrigeration cycle of acar air-conditioner, and constitutes a multi-flow type heat exchanger.

In this heat exchanger 1, a plurality of flat heat exchanging tubes 2arranged horizontally are disposed between a pair of vertical hollowheaders 4 and 4 arranged in parallel with each other with the ends ofthe tubes communicated with the hollow headers 4 and 4. Between theadjacent tubes 2 and outside the outermost tubes, a corrugated fin 3 isdisposed, and a side plate 10 is disposed outside the outermostcorrugated fin 3.

In this heat exchanger 1, as the tube 2, a tube made of aluminum(including its alloy, hereinafter simply referred to as “aluminum”) isused, and brazing material is covered on predetermined portions of eachcomponent. The tubes 2, fins 3, headers 4 and side plates 10 areprovisionally assembled into a provisional heat exchanger assembly, andthe assembly is integrally brazed in a furnace, whereby the entireassembly is integrally brazed.

As shown in FIG. 2, the tube 2 includes a tube core 2 a which is analuminum extruded member and a brazing layer 20 of an Al—Si alloy asbrazing alloy formed on at least one surface of the tube core.

As the core 2 a of the tube 2, an Al—Mn alloy with high pressureresistance (high strength) and high heat resistance, such as a JIS3003alloy, can be preferably used.

In this embodiment, by extruding this alloy, the tube core 2 a isformed.

It is preferable that the surface roughness Ry of the tube core 2 a isadjusted to less than 10 μm. That is, if the surface roughness Ryexceeds 10 μm, capillary attraction occurs on the surface of the tubecore 2 a, resulting in easy flow of brazing material, which in turncauses erosion to the tube by the brazing material. Thus, there is apossibility that brazing defects occur.

In this embodiment, the brazing layer 20 on the tube core 2 a is formedby forming a thermally sprayed layer 21 by making Al—Si alloy adhere tothe tube core by a thermal spraying method as shown in FIG. 3A, and thensmoothing the surface of the thermally sprayed layer 21 by compressingthe surface as shown in FIG. 3B.

In this embodiment, although a method of carrying out thermal sprayingof the Al—Si alloy as a brazing alloy to the surface of the tube core 2a is not limited to a specific one, in performing the thermal spraying,the thermal-spraying particles are sprayed to the tube core 2 a andquenched. In other words, the thermal spraying method of this inventionis not specifically limited so long as the aforementioned quenching canbe performed.

In this embodiment, in order to melt the thermal-spraying particles, thethermal-spraying temperature can be set to 3,000° C. or above, or anyknown means including a means using arc spraying can be adopted.

As a means for quenching the thermal-spraying particles, for example, itis preferable to employ a method in which the thermal-sprayingtemperature of the brazing alloy at the time of thermal spraying isadjusted to high, the hot thermal-spraying particles are sprayed on thetube core 2 a, and the heat of the thermal-spraying particles is made toemit to the tube core 2 a immediately after the reaching of thethermal-spraying particles to the core member 2 a to thereby quicklycool the thermal-spraying particles to a temperature of the tube coremember 2 a. For example, a means for cooling the thermal-sprayingparticles whose thermal-spraying temperature is 3,000° C. or above to800° C. or below by making them adhere the tube core 2 a can beemployed.

Concretely, in this embodiment, it is preferable to employ a means forquenching the thermally sprayed particles whose thermal-sprayingtemperature is high (4,500 to 5,500° C.) to the tube core temperature(400 to 500° C.) immediately after the extrusion by using an arcspraying method. In cases of flame spraying or high velocity flamespraying, since the thermal-spraying temperature is low (2,000 to 3,000°C.) as compared with arc spraying, there are possibilities that meltingof the thermal-spraying particles cannot fully be performed, orincreasing of the cooling rate is difficult and therefore quenchingcannot fully be performed. Furthermore, since they use brazing alloypowder, there is a possibility that the filling rate may deteriorate andtherefore it is not always suitable.

In this invention, however, if quenching can be performed irrespectiveof the thermal-spraying temperature and/or the tube core temperature,any kind of thermal spraying method can be employed. For example, thequenching of the thermal-spraying particles can be performed bycontrolling the thermal-spraying distance which will be explained below.

In this embodiment, in performing thermal-spraying, it is preferable toadjust the thermal-spraying distance from the spraying portion (sprayingposition) of the thermal spraying gun to the tube core surface (adheringposition) to 30 to 150 mm. That is, in cases where the thermal-sprayingdistance is within the aforementioned specified range, the speed ofthermal-spraying particles is high, and therefore the kinetic energy ofthe thermal-spraying particles is high. For this reason, since thethermal spraying particles change into a flat shape and adhere to thetube core surface when the thermal spraying particles are sprayed on thetube core surface, the filling rate becomes high and the heat releaseperformance of the thermal spraying particles to the tube core 2 a isalso improved, which enables sufficient quenching. Furthermore, thethermal-spraying distance is relatively short, i.e., 30 to 150 mm,resulting in a shorter arriving time of the thermal-spraying particlesto the tube core 2 a, or a shorter time from the thermal-spraying of thethermal-spraying particles to the cooling initiation, which in turn canperform the quenching more assuredly. In other words, in cases where thethermal-spraying distance is less than 30 mm or exceeds 150 mm, thespeed of the thermal-spraying particles becomes slower and thereforesufficient kinetic energy cannot be secured, causing a smaller amount ofdeformation of the thermal-spraying particles when the thermal-sprayingparticles adhere to the tube core, resulting in low filling rate.Furthermore, the heat releasing performance of the thermal-sprayingparticles to the tube core deteriorates, resulting in a failure ofquenching. Especially in cases where the thermal-spraying distanceexceeds 150 mm, during the flying of the thermal-spraying particles, thethermal-spraying particles different in flying speed may aggregate. Forexample, large particles and small particles will aggregate to becomelarge particles to be deposited. As a result, the thermally sprayedlayer 21 becomes hard and moderate brittleness cannot be secured. Thus,as will be detailed below, there is a possibility that smoothing of thethermally sprayed layer 21 cannot be attained effectively, and thereforeit is not preferable.

In cases where a brazing alloy is sprayed by an arc spraying method, forexample, a method of scanning a thermal spraying gun of an arc sprayingmachine with respect to the tube core 2 a or a method of carrying outthermal spraying while rewinding the core member 2 a rolled into acoiled form can be adopted. Furthermore, in cases where the tube core 2a is an extruded member, a method in which extrusion and thermalspraying are performed continuously while placing a thermal spraying gunarranged immediately after an extrusion die can be employed. Especiallyin cases where extrusion and thermal spraying are performedcontinuously, productive efficiency can be improved.

Furthermore, if an oxide film is formed on thermal-spraying particles atthe time of thermal spraying processing, the surface of thethermal-spraying particle hardens, resulting in decreased deformation ofthe thermal-spraying particle to be caused by colliding against the tubecore 2 a, which may cause deterioration of the filling rate. For thisreason, in order to prevent the formation of an oxide film onthermal-spraying particles, it is preferable to perform the thermalspraying processing in a non-oxidizing atmosphere, such as a nitrogenatmosphere or an argon atmosphere. From the economical view point, it ispreferable to perform the thermal spraying in a nitrogen atmosphere.

The thermally sprayed layer 21 can be formed only on one surface of thetube core 2 a, and also can be formed on both surfaces. Needless to say,in cases where the thermally sprayed layer 21 is formed on both surfacesof the tube core, it is preferable to arrange thermal spraying guns atupper and lower sides of the tube core 2 a.

In this embodiment, although the content of Si in the thermally sprayedlayer 21 is not specifically limited, in order to secure good brazingperformance, it is preferable to adjust the Si content to 6 to 15 mass%.

It is preferable that the thermally sprayed layer 21 contains Zn inorder to form a sacrificial protection layer on the surface of the tube.The Zn content in the thermally sprayed layer 21 is preferably adjustedto 1 to 30 mass %.

Furthermore, it is preferable that the thermally sprayed layer 21contains Cu within the range of 0.1 to 1 mass % for the purpose ofpotential adjustment, etc.

Furthermore, in this embodiment, the thermally sprayed layer 21 maycontain other elements, such as Fe, Mn, In, Sn, Ni, Ti, and Cr, as longas it is within the range that affects neither brazing performance norcorrosion resistance.

In this embodiment, after forming a thermally sprayed layer 21 on thetube core 2 a as shown in FIG. 3A, the surface of the thermally sprayedlayer 21 is smoothed to form a brazing layer 20 as shown in FIG. 3B.Thus, a heat exchanger tube 2 is obtained.

Although the method of smoothing the surface of the thermally sprayedlayer 2 is not specifically limited, a pressing method using reductionrolls and a cutting method such as scalping (trimming) can beexemplified. Among other things, a method of smoothing using reductionrolls is preferably employed since the method can improve theproductivity by consecutive operation.

This smoothing processing is preferably performed at the tube correctingstep. That is, as described above, in cases where the extrusion step ofextruding the tube core 2 a and the thermal spraying step of thermallyspraying the brazing material to the extruded tube member (tube core)are performed continuously, it is usually performed that the extrudedtube member after the brazing material thermal spraying is rolled into acoiled form and thereafter the thermally sprayed tube is cut into apredetermined size while being unwinding in the following tubecorrecting step to thereby manufacture heat exchanger tubes 2. At thetube correcting step, by performing the smoothing processing usingreduction rolls, smoothing processing can be performed simultaneouslywith the tube correcting processing.

In this embodiment, the surface roughness Ry of the smoothed brazinglayer 20 is preferably adjusted to 50 μm or less, more preferably to 40μm or less. That is, in cases where the surface roughness falls withinthe specified range, the fin 3 can be brazed to the brazing layer 20 ina balanced manner, which can prevent occurrence of brazing defects suchas fin detachment.

In this embodiment, since the thermal-spraying particles are sprayed ina molten state and then quenched at the aforementioned thermal sprayingprocessing, moderate brittleness can be given to the thermally sprayedlayer 21. Therefore, as shown in FIG. 3B, the crushing of the brittlepeak portions of the thermally sprayed layer 21 can be evenly performedover the entire region with rollers, etc. Thus, the surface of thethermally sprayed layer 21 (surface of the brazing layer) can beassuredly formed to have a desired smooth surface. Furthermore, sincecompressive deformation of only the thermally sprayed layer 21 can beperformed appropriately, the volume rate (filling rate) of the brazingmaterial in the entire brazing layer (apparent brazing layer) containingvoids can be improved, resulting in a sufficient amount of brazingmaterial on the tube required to perform brazing.

In this embodiment, the filling rate of the brazing material in thebrazing layer 20 is preferably adjusted to 40% or more, more preferably60% or more. Securing the filling rate within the aforementioned rangesecures a sufficient amount of the brazing material, which effectivelyprevents occurrence of brazing defects such as fin detachment.

In cases where quenching of the thermal-spraying particles is inadequateor a part of the thermal-spraying particles (thermal-spraying powder) isin a non-molten state at the time of thermal spraying processing, therigidity of the thermally sprayed layer 121 becomes high excessively asshown in FIG. 4A. As a result, even if the tube core 2 a having thethermally sprayed layer 121 of high rigidity is rolled with reductionrollers, as shown in this FIG. 4B, the tube core 2 a is deformed withoutcausing any deformation of the thermally sprayed layer 121, which maycause deteriorated quality. Furthermore, since the thermally sprayedlayer 121 is not compressed, the filling rate of the brazing material inthe thermally sprayed layer 121 cannot be improved, which may make itdifficult to secure the necessary amount of brazing material requiredfor brazing.

In this embodiment, it is preferable to adjust the average equivalentdiameter of the Si crystallization in the brazing layer 20 to 1 μm orless. That is, in cases where the dispersibility of Si in the brazinglayer 20 is good and the brazing performance is good, Si crystallizationbecomes small. Also in cases where the brazing alloy is fully molten atthe thermal spraying step and quenching is fully made and therefore thethermal-spraying particles has moderate brittleness, the crystallizationof Si becomes small. Accordingly, in this embodiment, the particlediameter of Si crystallization is preferable small. Concretely, it ispreferable to adjust the average equivalent diameter of Sicrystallization to 1 μm or less.

Although the thickness (average thickness) of the brazing layer 20 isnot specifically limited, it is preferable to adjust the thickness to 3to 50 μm. More preferably, the lower limit is adjusted to 5 μm or moreand the upper limit to 30 μm or less. That is, in cases where thethickness of the brazing layer 20 is adjusted within the aforementionedrange, the joining of the tube 2 and the fin 3 can be performedassuredly, and fin detachment, etc., can be prevented effectively.

The heat exchanger tube 2 of this embodiment is used together with otherheat exchanger components, such as hollow headers 4 and 4, corrugatedfins 3 and side plates 10, and is assembled into a provisional heatexchanger assembly. Thereafter, flux is applied to this assembly anddried. Then, the assembly is heated in a furnace of a nitrogen gasatmosphere to thereby integrally braze the components. Thus, a heatexchanger 1 is manufactured.

The obtained heat exchanger 1 is free from brazing defects such as findetachment, and is excellent in joined strength.

That is, in the heat exchanger tube 2 of this embodiment, since thebrazing layer 20 is obtained by smoothing the surface of the thermallysprayed layer 21 formed by the thermal spraying of brazing alloy, thefin 3 can be joined to the entire surface of the brazing layer 20 in abalanced manner, which in turn can assuredly prevent brazing defectssuch as fin detachment.

Especially in this embodiment, if the surface roughness Ry of the tubecore 2 a is adjusted to less than 10 μm, the brazing layer 20 is securedto the entire surface of the tube core 2 a in a stable manner.Therefore, unexpected flowing of the molten brazing material during thebrazing can be effectively prevented, which can assuredly preventoccurrence of defects such as erosion to the tube of the brazingmaterial.

Moreover, in this embodiment, since the brazing layer 20 is formed bycompressing the thermally sprayed layer 21, the brazing material fillingrate of the brazing layer 20 can be improved. Therefore, sufficientamount of brazing material for the brazing layer 20 can be secured,which can assuredly prevent occurrence of brazing defects due toshortage of brazing material.

Furthermore, in this embodiment, since fully molten thermal sprayingparticles are quenched, moderate brittleness can be given to thethermally sprayed layer 21. Therefore, at the time of smoothing thethermally sprayed layer 21 with reduction rollers, etc., only thethermally sprayed layer 21 can be compressed into a desired compressedshape. Thus, crush deformation of the tube core 2 a can be preventedeffectively, resulting in high quality.

In addition, in this embodiment, in cases where the surface roughness Ryof the brazing layer 20 is adjusted to below the specific value, the fin3 can be brazed to the brazing layer 20 in a balanced manner, which canmore assuredly prevent occurrence of brazing defects such a findetachment.

EXAMPLE

Hereafter, examples related to the present invention and comparativeexamples for verifying the effects of the invention will be explained.

TABLE 1 Surface Thermal spraying processing roughness ThermalThermal-spraying Smoothing of Filling Average of core Thermal sprayingThermal Thermal particles brazing layer rate of equivalent memberspraying tempera- spraying spraying Molten Cooling (surface brazingdiameter of Si (Ry) method ture distance environment state^(*1)rate^(*2) roughness Ry) material crystallization Example 1 10 μm  Arcthermal 5,000° C. 120 mm Air Molten Quenching Smoothed 50% 0.7 μmspraying (40 μm) Example 2 8 μm Arc thermal 5,500° C.  60 mm NitrogenMolten Quenching Smoothed 50% 0.1 μm spraying (37 μm) Example 3 7 μm Arcthermal 4,800° C.  60 mm Nitrogen Molten Quenching Smoothed 60% 0.5 μmspraying (35 μm) Example 4 8 μm Arc thermal 5,000° C.  80 mm Air MoltenQuenching Smoothed 50% 0.4 μm spraying (40 μm) Example 5 8 μm Arcthermal 4,800° C. 120 mm Nitrogen Molten Quenching Smoothed 40% 0.8 μmspraying (40 μm) Example 6 8 μm Arc thermal 5000° C. 100 mm NitrogenMolten Quenching Smoothed 50% 0.6 μm spraying (42 μm) Com. Ex. 1 8 μmArc thermal 5,000° C. 150 mm Air Molten Quenching Non-smoothed 30% 0.9μm spraying (60 μm) Com. Ex. 2 15 μm  Flame thermal 2,800° C. 150 mm AirPartially Non- Smoothed 30% 1.5 μm spraying not molten quenching (40 μm)Com. Ex. 3 10 μm  Flame thermal 2,500° C. 200 mm Air Partially Non-Non-smoothed 20%   2 μm spraying not molten quenching (60 μm) Com. Ex. 440 μm  Arc thermal 5,000° C. 120 mm Air Molten Quenching Non-smoothed20% 0.7 μm spraying (60 μm) Com. Ex. 5 30 μm  Flame thermal 3,000° C.250 mm Air Molten Non- Smoothed 40% 1.8 μm spraying quenching (60 μm)Com. Ex. 6 8 μm HVOF thermal 2,600° C. 100 mm Air Partially QuenchingSmoothed 50%   2 μm spraying not molten (65 μm) ^(*1)“Molten”: thethermal spraying temperature is 3,000° C. or above; “Partially notmolten”: below 3,000° C. ^(*2)“Quenching”: the temperature differencebetween the thermal-spraying particles and the extruded tube material is2,500° C. or above; “Non-quenching”: below 2,500° C.

Example 1

As shown in Table 1, a flat multi-bored extruded tube (tube core) 16 mmwidth, 3 mm height and 0.5 mm wall thickness was extruded with anextruder using extrusion material of an Al alloy (Cu: 0.4 mass %, Mn:0.21 mass %; Al: balance). The surface roughness Ry of the obtained tubecore was 10 μm.

An Al—Si alloy was thermally sprayed to the upper and lower surfaces ofthe extruded tube through thermal spraying guns of an arc sprayingmachine arranged at the upper and lower sides of the outlet of theextruder, to thereby form a thermally sprayed layer. In this thermalspraying processing, the thermal-spraying distance was adjusted to 120mm in the atmosphere.

The molten thermal-spraying particles to be sprayed against the tubecore adhered to the tube core by being cooled from the thermal-sprayingtemperature to a temperature of the tube core by being absorbed in heatby the tube core when they reached the tube core.

In Table 1, as for the cooling degree of the thermal-spraying particles,in cases where the difference between the thermal-spraying temperatureof the thermal-spraying particles and the temperature of the tube corewas 2,500° C. or more, it was denoted as “quenching”, and in cases whereit was less than 2,500° C., it was denoted as “non-quenching.” In thecase of Example 1, the thermal-spraying temperature of thethermal-spraying particles was 5,000° C., the temperature of the tubecore was 400° C., and those temperature difference was 4,600° C.Accordingly, the cooling degree in Example was quenching.

After performing the thermal spraying, the aforementioned extruded tubewith a thermally sprayed layer was immersed in a cooling bath to becooled, and then continuously rolled into a coil form.

Thereafter, while recoiling, the coil foamed tube was pressed withreduction rollers to compress the thermally sprayed layer to smooth thesurface, thereby forming a brazing layer 50% in net filling rate of thebrazing material (apparent filling rate of the brazing material to thebrazing layer), 20 μm in thickness, and 40 μm in surface roughness (Ry),and then cut into a predetermined length to obtain heat exchanger tubes.In these tubes, the average equivalent diameter of Si crystallizationwas 0.7 μm.

Then, using the aforementioned heat exchanger tubes, the so-calledmulti-flow type aluminum heat exchanger (see FIG. 1) was provisionallyassembled. Slurry in which non-corrosive flux was suspended in water wassprayed to the heat exchanger provisional assembly and then dried. Then,the assembly was heated at 600° C. for 10 minutes in a nitrogen gasatmosphere furnace to integrally braze the components to thereby obtainthe heat exchanger in Example 1.

Example 2

As shown in table 1, against the extruded tube 8 μm in surface roughnessRy, thermal spraying was performed by an arc spraying method at thethermal-spraying temperature of 5,500° C. and the thermal-sprayingdistance of 60 mm in a nitrogen atmosphere. The tube member with thethermally sprayed layer was pressed with reduction rollers to form abrazing layer 50% in brazing material filling rate, 15 μm in thickness,37 μm in surface roughness Ry. Thus, the heat exchanger tube wasmanufactured in the same manner as mentioned above. In this tube, theaverage equivalent diameter of Si crystallization was 0.1 μm.

Then, a heat exchanger was manufactured using the heat exchanger tubesin the same manner as in the aforementioned Example.

Example 3

As shown in table 1, against the extruded tube 7 μm in surface roughnessRy, thermal spraying was performed by an arc spraying method at thethermal-spraying temperature of 4,800° C. and the thermal-sprayingdistance of 60 mm in a nitrogen atmosphere. The tube member with thethermally sprayed layer was pressed with reduction rollers to form abrazing layer 60% in brazing material filling rate, 20 μm in thickness,35 μm in surface roughness Ry. Thus, the heat exchanger tube wasmanufactured in the same manner as mentioned above. In this tube, theaverage equivalent diameter of Si crystallization was 0.5 μm.

Then, a heat exchanger was manufactured using the heat exchanger tubesin the same manner as in the aforementioned Example.

Example 4

As shown in table 1, against the extruded tube 8 μm in surface roughnessRy, thermal spraying was performed by an arc spraying method at thethermal-spraying temperature of 5,000° C. and the thermal-sprayingdistance of 80 mm in an atmosphere. The tube member with the thermallysprayed layer was pressed with reduction rollers to form a brazing layer50% in brazing material filling rate, 30 μm in thickness, 40 μm insurface roughness Ry. Thus, the heat exchanger tube was manufactured inthe same manner as mentioned above. In this tube, the average equivalentdiameter of Si crystallization was 0.4 μm.

Then, a heat exchanger was manufactured using the heat exchanger tubesin the same manner as in the aforementioned Example.

Example 5

As shown in table 1, against the extruded tube 8 μm in surface roughnessRy, thermal spraying was performed by an arc spraying method at thethermal-spraying temperature of 4,800° C. and the thermal-sprayingdistance of 120 mm in a nitrogen atmosphere. The tube member with thethermally sprayed layer was pressed with reduction rollers to form abrazing layer 40% in brazing material filling rate, 20 μm in thickness,40 μm in surface roughness Ry. Thus, the heat exchanger tube wasmanufactured in the same manner as mentioned above. In this tube, theaverage equivalent diameter of Si crystallization was 0.8 μm.

Then, a heat exchanger was manufactured using the heat exchanger tubesin the same manner as in the aforementioned Example.

Example 6

As shown in table 1, against the extruded tube 8 μm in surface roughnessRy, thermal spraying was performed by an arc spraying method at thethermal-spraying temperature of 5,000° C. and the thermal-sprayingdistance of 100 mm in a nitrogen atmosphere. The tube member with thethermally sprayed layer was pressed with reduction rollers to form abrazing layer 50% in brazing material filling rate, 25 μm in thickness,42 μm in surface roughness Ry. Thus, the heat exchanger tube wasmanufactured in the same manner as mentioned above. In this tube, theaverage equivalent diameter of Si crystallization was 0.6 μm.

Then, a heat exchanger was manufactured using the heat exchanger tubesin the same manner as in the aforementioned Example.

Comparative Example 1

As shown in table 1, against the extruded tube 8 μm in surface roughnessRy, thermal spraying was performed by an arc spraying method at thethermal-spraying temperature of 5,000° C. and the thermal-sprayingdistance of 150 mm in an atmosphere. Without performing the smoothing ofthe thermally sprayed layer, the brazing layer 30% in brazing materialfilling rate, 60 μm in thickness, 60 μm in surface roughness Ry wasformed. Thus, the heat exchanger tube was manufactured in the samemanner as mentioned above. In this tube, the average equivalent diameterof Si crystallization was 0.9 μm.

Then, a heat exchanger was manufactured using the heat exchanger tubesin the same manner as in the aforementioned Example.

Comparative Example 2

As shown in table 1, against the extruded tube 15 μm in surfaceroughness Ry, thermal spraying was performed by a flame spraying methodat the thermal-spraying temperature of 2,800° C. and thethermal-spraying distance of 150 mm in an atmosphere. The tube memberwith the thermally sprayed layer was pressed with reduction rollers toform a brazing layer 30% in brazing material filling rate, 40 μm inthickness, 40 μm in surface roughness Ry. Thus, the heat exchanger tubewas manufactured in the same manner as mentioned above. In this tube,the average equivalent diameter of Si crystallization was 1.5 μm.

Then, a heat exchanger was manufactured using the heat exchanger tubesin the same manner as in the aforementioned Example.

Comparative Example 3

As shown in table 1, against the extruded tube 10 μm in surfaceroughness Ry, thermal spraying was performed by a flame spraying methodat the thermal-spraying temperature of 2,500° C. and thethermal-spraying distance of 200 mm in an atmosphere. Without performingthe smoothing of the thermally sprayed layer, the brazing layer 20% inbrazing material filling rate, 40 μm in thickness, 60 μm in surfaceroughness Ry was formed. Thus, the heat exchanger tube was manufacturedin the same manner as mentioned above. In this tube, the averageequivalent diameter of Si crystallization was 2 μm.

Then, a heat exchanger was manufactured using the heat exchanger tubesin the same manner as in the aforementioned Example.

Comparative Example 4

As shown in table 1, against the extruded tube 40 μm in surfaceroughness Ry, thermal spraying was performed by an arc spraying methodat the thermal-spraying temperature of 5,000° C. and thethermal-spraying distance of 120 mm in an atmosphere. Without performingthe smoothing of the thermally sprayed layer, the brazing layer 20% inbrazing material filling rate, 40 μm in thickness, 60 μm in surfaceroughness Ry was formed. Thus, the heat exchanger tube was manufacturedin the same manner as mentioned above. In this tube, the averageequivalent diameter of Si crystallization was 0.7 μm.

Then, a heat exchanger was manufactured using the heat exchanger tubesin the same manner as in the aforementioned Example.

Comparative Example 5

As shown in table 1, against the extruded tube 30 μm in surfaceroughness Ry, thermal spraying was performed by a flame spraying methodat the thermal-spraying temperature of 3,000° C. and thethermal-spraying distance of 250 mm in an atmosphere. Without performingthe smoothing of the thermally sprayed layer, the brazing layer 40% inbrazing material filling rate, 80 μm in thickness, 60 μm in surfaceroughness Ry was formed. Thus, the heat exchanger tube was manufacturedin the same manner as mentioned above. In this tube, the averageequivalent diameter of Si crystallization was 1.8 μm.

Then, a heat exchanger was manufactured using the heat exchanger tubesin the same manner as in the aforementioned Example.

Comparative Example 6

As shown in table 1, against the extruded tube 8 μm in surface roughnessRy, thermal spraying was performed by a HVOF (high-speed flame) splayingmethod at the thermal-spraying temperature of 2,600° C. and thethermal-spraying distance of 100 mm in an atmosphere. Without performingthe smoothing of the thermally sprayed layer, the brazing layer 50% inbrazing material filling rate, 80 μm in thickness, 65 μm in surfaceroughness Ry was formed. Thus, the heat exchanger tube was manufacturedin the same manner as mentioned above. In this tube, the averageequivalent diameter of Si crystallization was 2 μm.

Then, a heat exchanger was manufactured using the heat exchanger tubesin the same manner as in the aforementioned Example.

<Evaluation>

As for each heat exchanger of the aforementioned Examples andComparative Examples, the joining rate between the fin and the tube wasmeasured. In the evaluation, “⊚” denotes that the joining rate betweenthe fin and the tube was 95% or more; “∘” denotes that the joining ratebetween the fin and the tube was 90% or more but less than 95%; “Δ”denotes that the joining rate between the fin and the tube was 60% ormore but less than 90%; “X” denotes that the joining rate between thefin and the tube was less than 60% or fin detachment was occurred. Theevaluation results are collectively shown in the following Table 2.

TABLE 2 Evaluation Fin/tube joining rate Remarks Example 1 ⊚ — Example 2⊚ — Example 3 ⊚ — Example 4 ⊚ — Example 5 ◯ — Example 6 ⊚ — Com. Example1 X — (fin detachment) Com. Example 2 ◯ Deformed in cross-section oftube core Com. Example 3 X — (fin detachment) Com. Example 4 X Erosionof tube core by (fin detachment) brazing material Com. Example 5 ◯Deformed in cross-section of tube core Com. Example 6 ◯ Deformed incross-section of tube core

As will be clear from Table 2, in Examples 1 to 6 satisfying therequirements of this invention, brazing defects such as fin detachmentwas prevented, and good brazing performance was secured. Furthermore, inExamples 1 to 6, tube deformation due to the smoothing was assuredlyprevented, resulting in high quality.

To the contrary, in Comparative Examples deviating from the requirementsof this invention, good performance was not secured. For example, likein Comparative Examples 1, 3 or 4 in which smoothing of the thermallysprayed layer was not performed and the brazing material filling ratewas low, fin detachment occurred and good brazing performance was notsecured. Furthermore, in cases where melting of the thermal-sprayingparticles at the time of thermal spraying was inadequate like inComparative Examples 2, 5 and 6, or in cases where quenching wasinadequate, the tube itself was crushed at the time of smoothing thethermally sprayed layer, causing deterioration of quality.

INDUSTRIAL APPLICABILITY

This invention can be applied to an aluminum heat exchanger for use in acar air-conditioning refrigeration cycle, a heat exchanger tube used forsuch a heat exchanger, and a manufacturing method thereof.

While the present invention may be embodied in many different forms, anumber of illustrative embodiments are described herein with theunderstanding that the present disclosure as to be considered asproviding examples of the principles of the invention and such examplesare not intended to limit the invention to preferred embodimentsdescribed herein and/or illustrated herein.

While illustrative embodiments of the intention have been describedherein, the present invention is not limited to the various preferredembodiments described herein, but includes any and all embodimentshaving equivalent elements, modifications, omissions, combinations(e.g., of aspects across various embodiments), adaptations and/oralterations as would be appreciated by those in the art based on thepresent disclosure. The limitations in the claims are to be interpretedbroadly based on the language employed in the claims and not limited toexamples described in the present specification or during theprosecution of the application, which examples are to be construed asnon-exclusive. For example, in the present disclosure, the term“preferably” is non-exclusive and means “preferably, but not limitedto.” In this disclosure and during the prosecution of this application,means-plus-function or step-plus-function limitations will only beemployed where for a specific claim limitation all of the followingconditions are present in that limitation: a) “means for” or “step for”is expressly recited; b) a corresponding function is expressly recited;and c) structure, material or acts that support that structure are notrecited. In this disclosure and during the prosecution of thisapplication, the terminology “present invention” or “invention” may beused as a reference to one or more aspect within the present disclosure.The language present invention or invention should not be improperlyinterpreted as an identification of criticality, should not beimproperly interpreted as applying across all aspects or embodiments(i.e., it should be understood that the present invention has a numberof aspects and embodiments), and should not be improperly interpreted aslimiting the scope of the application or claims. In this disclosure andduring the prosecution of this application, the terminology “embodiment”can be used to describe any aspect, feature, process or step, anycombination thereof, and/or any portion thereof, etc. In some examples,various embodiments may include overlapping features. In this disclosureand during the prosecution of this case, the following abbreviatedterminology may be employed: “e.g.” which means “for example;” and “NB”which means “note well.”

1. A method of manufacturing an aluminum heat exchanger tube, the methodcomprising the steps of: in forming a thermally sprayed layer on asurface of an aluminum flat tube by thermally spraying Al—Si alloythermal-spraying particles, quenching the thermally sprayedthermal-spraying particles in a molten state to make them adhere to atube core; and smoothing a surface of the thermally sprayed layer toform a brazing layer.
 2. The method of manufacturing an aluminum heatexchanger tube as recited in claim 1, wherein surface roughness (Ry) ofthe tube core is adjusted to less than 10 μm.
 3. The method ofmanufacturing an aluminum heat exchanger tube as recited in claim 1 or2, wherein surface roughness (Ry) of the brazing layer is adjusted toless than 50 μm.
 4. The method of manufacturing an aluminum heatexchanger tube as recited in any one of claims 1 to 3, wherein athermal-spraying temperature of the thermal-spraying particles isadjusted to 3,000° C. or above.
 5. The method of manufacturing analuminum heat exchanger tube as recited in any one of claims 1 to 4,wherein the thermal-spraying particles are cooled to 800° C. or belowafter reaching the tube core.
 6. The method of manufacturing an aluminumheat exchanger tube as recited in any one of claims 1 to 5, wherein inthermally spraying the thermal-spraying particles, a temperaturedifference between the thermal-spraying particles in a molten state andthe thermal-spraying particles reached the tube core in a cooled stateis adjusted to 2500° C. or more.
 7. The method of manufacturing analuminum heat exchanger tube as recited in any one of claims 1 to 6,wherein in thermally spraying the thermal-spraying particles, thethermal-spraying particles reached the tube core are cooled by releasingthe heat to the tube core.
 8. The method of manufacturing an aluminumheat exchanger tube as recited in any one of claims 1 to 7, wherein anaverage equivalent diameter of Si crystallization particles in thethermally sprayed layer is adjusted to 1 μm or less.
 9. The method ofmanufacturing an aluminum heat exchanger tube as recited in any one ofclaims 1 to 8, wherein an apparent volume rate (filling rate) of thebrazing material in the brazing layer is adjusted to 40% or more. 10.The method of manufacturing an aluminum heart exchanger tube as recitedin any one of claims 1 to 9, wherein in thermally spraying thethermal-spraying particles, a thermal-spraying distance from a sprayingposition of the thermal-spraying particles to an adhering position onthe tube core is adjusted to 30 to 150 mm.
 11. The method ofmanufacturing an aluminum heart exchanger tube as recited in any one ofclaims 1 to 10, wherein thermal spraying of the thermal-sprayingparticles is performed by an arc spraying method.
 12. The method ofmanufacturing an aluminum heat exchanger tube as recited in any one ofclaims 1 to 11, wherein a Si content in the thermally sprayed layer isadjusted to 6 to 15 mass %.
 13. The method of manufacturing an aluminumheart exchanger tube as recited in any one of claims 1 to 12, wherein anaverage thickness of the brazing layer is adjusted to 3 to 50 μm. 14.The method of manufacturing an aluminum heart exchanger tube as recitedin any one of claims 1 to 13, wherein the surface of the thermallysprayed layer is pressed with reduction rolls to smooth the surface. 15.The method of manufacturing an aluminum heat exchanger tube as recitedin any one of claims 1 to 14, wherein Zn is contained to the thermallysprayed layer.
 16. The method of manufacturing an aluminum heatexchanger tube as recited in any one of claims 1 to 15, wherein Zn andCu are contained to the thermally sprayed layer.
 17. The method ofmanufacturing an aluminum heat exchanger tube as recited in any one ofclaims 1 to 16, wherein the tube core is formed by extrusion, and thethermal-spraying particles are thermally sprayed to the tube coreimmediately after the extrusion.
 18. The method of manufacturing analuminum heat exchanger tube as recited in any one of claims 1 to 17,wherein each thermal-spraying particle adheres to the surface of thetube core in a flat state.
 19. The method of manufacturing an aluminumheat exchanger tube as recited in any one of claims 1 to 18, wherein thethermal-spraying particles are thermally sprayed under a non-oxidizingatmosphere.
 20. A method of manufacturing an aluminum heat exchangertube, the method comprising the steps of: in forming a thermally sprayedlayer on a surface of an aluminum flat tube by thermally spraying Al—Sialloy thermal-spraying particles, thermally spraying thethermal-spraying particles to a tube core by an arc spraying method, andquenching the thermally sprayed thermal-spraying particles to 800° C. orbelow; and smoothing a surface of the thermally sprayed layer to form abrazing layer.
 21. A method of manufacturing an aluminum heat exchangertube, the method comprising the steps of: in forming a thermally sprayedlayer on a surf ace of an aluminum flat tube by thermally spraying Al—Sialloy thermal-spraying particles, performing the thermal spraying by arcspraying in which a thermal-spraying distance from a spraying positionof the thermal-spraying particles to an adhering position of the tubecore is adjusted to 30 to 150 mm; and smoothing a surface of thethermally sprayed layer to form a brazing layer.
 22. A method ofmanufacturing an aluminum ha at exchanger tube, the method comprisingthe steps of: in forming a thermally sprayed layer on a surface of analuminum flat tube by thermally spraying Al—Si alloy thermal-sprayingparticles, thermally spraying the thermal-spraying particles with athermal-spraying temperature of 3,000° C. or above and cooling them to800° C. or below to make them adhere to a tube core; and smoothing asurface of the thermally sprayed layer to form a brazing layer.
 23. Amethod of manufacturing an aluminum heat exchanger tube, the methodcomprising the steps of: in forming a thermally sprayed layer on a surface of an aluminum flat tube by thermally spraying Al—Si alloythermal-spraying particles, thermally spraying the thermal-sprayingparticles in a molten state and cooling to make them adhere to a tubecore, and adjusting a temperature difference between thethermal-spraying particles in a molten state and the thermal-sprayingparticles after the cooling is adjusted to 2,500° C. or more; andsmoothing a surface of the thermally sprayed layer to form a brazinglayer.
 24. An aluminum heat exchanger tube manufactured by the method asrecited in any one of the claims 1 to
 23. 25. An aluminum heat exchangertube, comprising: an aluminum flat tube core; and a thermally sprayedlayer formed on a surface of the tube core by thermally sprayingthermal-spraying particles of molten Al—Si alloy, wherein a surface ofthe thermally sprayed layer is smoothed to form a brazing layer, andwherein an average equivalent diameter of Si crystallization particlesin the thermally sprayed layer is adjusted to 1 μm or less.
 26. Thealuminum heat exchanger tube as recited in claim 25, wherein an apparentvolume rate (filling rate) of the brazing material in the brazing layeris adjusted to 40% or more.
 27. An aluminum heat exchanger includingaluminum heat exchanger tubes and aluminum fins brazed to the tubes inan assembled state, wherein the heat exchanger tubes are manufactured bythe method as recited in any one of claims 1 to
 23. 28. An aluminum heatexchanger including a pair of aluminum headers and a plurality of heatexchanger tubes arranged in a longitudinal direction of the header witha fin interposed therebetween, end portions of the heat exchanger tubesbeing communicated with the headers, wherein the heat exchanger tubesare manufactured by the method as recited in any one of claims 1 to 23.29. A method of manufacturing an aluminum heat exchanger, the methodcomprising: a step of preparing an aluminum heat exchanger tubemanufactured by the method as recited in any one of claims 1 to 23; astep of preparing an aluminum fin; and a step of brazing the heatexchanger tube and the fin in an assembled state.
 30. A method ofmanufacturing an aluminum heat exchanger, the method comprising: a stepof preparing a plurality of aluminum heat exchanger tubes manufacturedby the method as recited in any one of claims 1 to 23; a step ofpreparing a plurality of aluminum fins; a step of preparing a pair ofheaders; a step of obtaining a provisional assembly in which theplurality of heat exchanger tubes arranged in a longitudinal directionof the header with the fin interposed therebetween are assembled withthe headers with end portions of each heat exchanging tube communicatedwith the headers; a step of integrally brazing adjacent heat exchangertubes and the fins by simultaneously brazing the provisional assembly.31. A refrigeration cycle in which refrigerant compressed by acompressor is condensed with a condensed, and the condensed refrigerantis decompressed by passing through a decompressor, and the decompressedrefrigerant is evaporated with an evaporator and returned to thecompressor, wherein the condenser is constituted by the aluminum heatexchanger as recited in claim 28.